Liquid crystal display device with data switching thin film transistor for inspection and inspection method thereof

ABSTRACT

A liquid crystal display device includes a pixel matrix where a plurality of gate lines and a plurality of data lines cross each other and a plurality of liquid crystal cells are arranged, first data switching thin film transistors respectively connected to data lines of a first group of the data lines, and second data switching thin film transistors respectively connected to data lines of a second group of the data lines.

This application claims the benefit of the Korean Patent Application No.P2005-051650 filed on Jun. 15, 2005 which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to a liquid crystal display device and testing methodthereof. Although the present invention is suitable for a wide scope ofapplications, it is particularly suitable for increasing yield bypreventing an unnecessary waste of parts.

2. Description of the Related Art

As the information society develops, the importance of a display deviceas a visual information transmission medium increases. A cathode raytube (CRT) or Braun tube is currently the typical display device.However, the CRT has problems in that its weight and size are too large.Unlike the CRT, various types of flat panel display devices have beendeveloped are light-weight and have a thin profile. These types of flatpanel display devices include liquid crystal display (LCD), fieldemission display FED, plasma display panel PDP, electro-luminescence EL,and other types of flat panel devices that are practical to use and onthe market.

The liquid crystal display device can satisfy the current trend inelectronic devices of being thin, light-weight, and small. As theefficiency in the productivity in LCD devices improves, LCD devices willrapidly supersedes the cathode ray tube in a many applications.

In general, there are two types of LCDs. The first type is an activematrix LCD and the second type is a passive matrix type. In a passivematrix type LCD, each of the cells are switched externally. In theactive matrix type LCD, each of the cell are switched internally by athin film transistor (TFT). The active matrix type LCD has advantages inthat picture quality is excellent and power consumption is low. Further,the active matrix type LCD can be manufactured so as to have a largesize and to have high resolution due to a recent advances in massproduction technology, which resulted from research and development. Aprocess for fabricating the active matrix type LCD can be divided intosubstrate cleaning, substrate patterning, alignment filmforming/rubbing, substrate bonding/liquid crystal injecting, mounting,inspecting and repairing. In the substrate cleaning process, impuritiescontaminated in a substrate surface are removed with a cleaningsolution.

The substrate patterning process is divided into an upper substrate (orcolor filter substrate) patterning and lower substrate (or TFT-arraysubstrate) patterning. A color filter, a common electrode and a blackmatrix are formed on an upper substrate in the upper substratepatterning. A signal wire lines, such as data lines and gate lines, areformed on a lower substrate, and a cell thin film transistor(hereinafter, referred to as “cell TFT”) is formed adjacent to acrossing of the data line and the gate line in the lower substratepatterning. And, a pixel electrode is formed at a pixel area between thegate line and the data line connected to a source electrode of the cellTFT.

In the alignment film forming/rubbing process, an alignment film isformed on at least one of the upper substrate and the lower substrate.Then, the alignment film is rubbed with a rubbing cloth. If alignmentfilms are formed on both of the substrates, the alignment films arerubbed in the same direction.

In the substrate bonding/liquid crystal injecting process, the uppersubstrate and the lower substrate are bonded with a sealant. Then, aliquid crystal and a spacer are injected through a liquid crystalinjection hole in the sealant. Subsequently, a sealing process isperformed on the liquid crystal injection hole.

In the mounting process of the liquid crystal display panel, a tapecarrier package (hereinafter, referred to as “TCP”) on which anintegrated circuit, such as a gate drive integrated circuit and a datadrive integrated circuit are mounted, is connected to a pad part of thelower substrate. The drive integrated circuit can also be directlymounted on the lower substrate by a chip-on-glass (hereinafter, referredto as “COG”) method other than a tape automated bonding method.

The inspecting process includes an electrical inspection performed afterforming the various signal lines and the pixel electrode on the lowersubstrate; an electrical inspection performed after the substratebonding/liquid crystal injecting process; and macrography inspection.

The repairing process performs restoration of a substrate or panel,which is judged to be repairable during the inspecting process. On theother hand, defective substrates which are judged to be unrepairable inthe inspecting process are disposed as a waste.

The electrical inspection after the substrate bonding/liquid crystalinjecting process is mainly composed of a picture quality inspectionthat includes a cross-talk inspection and a brightness inspection ofeach gray level. The electrical inspection is performed when a datadrive circuit and a gate drive circuit are connected to the signal lineof the TFT array substrate, as shown in FIGS. 1 and 2.

As shown in FIG. 1, an inspecting method of the related art connects adata switching TFT (hereinafter, referred to as “Tdata”) to lower endsof the data lines DL. Further, the related art inspecting methodattaches a gate switching TFT (hereinafter, referred to as “Tgate”) forsupplying an inspection gate pulse to the gate lines at the same time inthe gate lines GL. Furthermore, another switching TFT (hereinafter,referred to as “Tmuxe”) is connected to the top ends of the data linesDL of a pixel matrix array in which the liquid crystal cells Clc and thecell TFT's are formed, to act to supply a data voltage, which issupplied from output terminals of the data drive circuit 10 of the TCPor COG A set of external contact pads 11 includes a MUX1 pad, a MUX2 padand a MUX3 pad for controlling the Tmuxes; a VEGATE pad for supplying avoltage to a gate terminal of the Tgate; a VGATE pad for supplying agate high voltage and a gate low voltage to a source terminal of theTgate; a VEDATA pad for supplying a voltage to a gate terminal of theTdata; and a VDATA pad for supplying a test data voltage to sourceterminals of the Tdatas.

If the set of the external contact pads 11 is connected to outputterminals of a test jig, a test data voltage can be supplied to the datalines DL through the VDATA pad via Tdata, and a gate high voltage issupplied to the gate lines GL through the VGATE pad via the Tgate. As aresult, the TFT's of the pixel array are turned on so as to apply thetest data voltage to the liquid crystal cells, thereby enablinginspection of whether there is a gray level expression defect in any ofthe liquid crystal cells.

During this inspecting method, the gate drive circuits 13 in a TCP canbe attached to the liquid crystal display panel, as shown in FIG. 2, tosequentially supply a gate pulse to the gate lines GL, therebysequentially selecting the liquid crystal cells of a horizontal line towhich the test data voltage is to be supplied. Further, for inspectingthe cross-talk, the inspecting method of the related art displays a midgray level on the outer perimeter with black on the inside followed bywhite in the pixel matrix array of the liquid crystal display panel, asshown in FIG. 3. Thus, at least two different test data are supplied tothe data lines DL, but the same data cannot be supplied to the datalines by the VDATA via Tdata formed in the liquid crystal display panelof FIGS. 1 and 2. Accordingly, a data drive circuit 10 is connected tothe Tmux of the liquid crystal display panel in a COG or TCP form. Inother words, according to the related art inspecting method, whenperforming the cross-talk inspection, the data drive circuit must beattached to the liquid crystal display panel in the TCP or COG form todetermine whether or not there is a cross-talk defect. However, it isinevitable that the TCP or COG attached to the liquid crystal displaypanel, which is judged to be defective by a cross-talk inspection, willhave to be discarded because it is attached to a defective liquidcrystal display panel. Thus, data drive circuits will be wasted and thusdecrease overall yield of data drive circuits.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay device and testing method thereof that substantially obviatesone or more of the problems due to limitations and disadvantages of therelated art.

An object of the present invention to provide a liquid crystal displaydevice that increases yield by preventing an unnecessary waste of partsfor a cross-talk inspection.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

In order to achieve these and other objects of the invention, a liquidcrystal display device includes a pixel matrix where a plurality of gatelines and a plurality of data lines cross each other and a plurality ofliquid crystal cells are arranged, first data switching thin filmtransistors respectively connected to data lines of a first group of thedata lines, and second data switching thin film transistors respectivelyconnected to data lines of a second group of the data lines.

In another aspect, a liquid crystal display device includes a pixelmatrix where a plurality of gate lines and a plurality of data linescross each other and a plurality of liquid crystal cells are arranged, agate drive circuit for supplying a scan pulse to the gate lines, firstdata switching thin film transistors respectively connected to a firstgroup of the data lines, second data switching thin film transistorsrespectively connected to a second group of the data lines, a firstexternal wire line connected to data input terminals of the first dataswitching thin film transistors, a second external wire line connectedto data input terminals of the second data switching thin filmtransistors, a third external wire line connected to control terminalsof the first and second data switching thin film transistors, a firstexternal pad for supplying first data to the first external wire line, asecond external pad for supplying second data to the second externalwire line; and a third external pad for supplying control data to thethird external wire line.

An inspection method of a liquid crystal display device according toanother aspect of the present invention includes the steps of forming apixel matrix in which a plurality of gate lines and a plurality of datalines cross each other and a plurality of liquid crystal cells arearranged, first data switching thin film transistors respectivelyconnected to data lines of a first group of the data lines, second dataswitching thin film transistors respectively connected to data lines ofa second group of the data lines, a first external wire line connectedto data input terminals of the first data switching thin filmtransistors, a second external wire line connected to data inputterminals of the second data switching thin film transistors, a thirdexternal wire line connected to control terminals of the first andsecond data switching thin film transistors, a first external pad forsupplying first data to the first external wire line, a second externalpad for supplying second data to the second external wire line, and athird external pad for supplying control data to the third external wireline, connecting a gate drive circuit for supplying a scan pulse to thegate lines to the gate lines, and supplying the first and second data tothe external pads to display a window pattern on the pixel matrix andjudging whether there is a cross-talk defect.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a plan view of a related art liquid crystal display panel;

FIG. 2 is a plan view of another related art liquid crystal displaypanel;

FIG. 3 is a diagram representing a test window pattern for cross-talkinspection;

FIG. 4 is a plan view of a liquid crystal display panel according to anembodiment of the present invention;

FIG. 5 is a diagram representing a test window pattern according to anembodiment of the present invention; and

FIG. 6 is a driving waveform diagram of line inversion for realizing thetest window pattern shown in FIG. 5;

FIG. 7 is a driving waveform diagram of dot inversion for realizing thetest window pattern shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. With reference to FIGS. 4 to 7, embodiments of the presentinvention will be explained as follows.

As shown in FIG. 4, a liquid crystal display panel according to anembodiment of the present invention includes a pixel matrix array wherea plurality of data lines DL and a plurality of gate lines GL cross eachother, a plurality of cell TFT's are arranged adjacent to the crossings,and liquid crystal cells are arranged in a matrix shape; a dataswitching TFT Tdata connected to a lower end of each data line DL; agate TFT Tgate connected to a one end of the gate line GL; a gate drivecircuit 7 in a TCP or COG form connected to the other end of the gatelines GL; and a set of external contact pads 1 for receiving testsignals from an inspection jig.

The set of external contacts pad 1 includes a MUX1 pad, a MUX2 pad and aMUX3 pad for controlling a Tmux; a VEGATE pad for supplying a voltage toa gate terminal of the Tgate; a VGATE pad for supplying a gate highvoltage and a gate low voltage to a source terminal of the Tgate; aVEDATA pad for supplying a voltage to a gate terminal of the Tdata; anda VDATA1 pad and a VDATA2 pad divided into two for supplying a test datavoltage to source terminals of the Tdatas.

The gate drive circuit 7 includes a shift register having a levelshifter for shifting a swing width of a scan pulse to a level suitablefor driving the liquid crystal cell Clc and an output buffer. The gatedrive circuit 7 receives a high potential power supply voltage VDD, alow potential power supply voltage VSS, clock signals GCLKS and a statpulse GVST through a gate pad group 8 to supply a scan pulse of gatehigh voltage to the gate line GL, thereby turning on the cell TFTsconnected to the gate line GL to select the liquid crystal cells Clc ofone horizontal line in which the data is to be displayed.

The substrate of the liquid crystal display panel includes firstexternal wire lines 6 for connecting the MUX1 pad, MUX2 pad and MUX3 padto a gate terminals of the Tmuxs: a second external wire line 5 forconnecting the VEGATE pad to a gate terminal of the Tgate; a thirdcontrol wire line 4 for connecting the VGATE pad to a source terminal ofthe Tgate; a third external wire line for connecting the VEDATA to agate terminal of the Tdata; a fourth external wire line 2A forconnecting the VDATA1 pad to source terminals of Tdatas on the sides ofthe liquid crystal display panel that are connected to the data lines DLon the sides of the liquid crystal display panel; and a fifth externalwire line 2B for connecting the VDATA2 pad to a source terminal ofTdatas at the middle of the liquid crystal display panel that areconnected to middle data lines DL within the pixel matrix.

In order to inspect an expressive capacity of each gray level, a testjig supplies the same test gray level data to the VDATA1 pad and theVDATA2 pad. And, in order to select a horizontal line to which the testgray level data are supplied, the Tgate is turned on by a gate highvoltage and a gate control voltage generated from the test jig or thegate high voltage is sequentially supplied to the gate lines GL by thegate drive circuit. Then, the liquid crystal cells within the pixelmatrix displays the test gray level data, and an expressive capacity ofthe light output is automatically detected with an image pickup deviceor inspected with a naked eye.

The test cross-talk data for the cross-talk inspection is generated in awindow pattern as shown in FIG. 5. The “V” in FIG. 5 represents avertical direction and the “H” represents a horizontal direction. In thecase of a line inversion driving, a driving waveform of the testcross-talk data of FIG. 5 is shown in FIG. 6. The line inversion drivingsupplies the data of the same polarity to the liquid crystal cells ofthe same horizontal line, but on the other hand, it supplies the data ofpolarities which are different from each other to the liquid crystalcells of the adjacent horizontal lines. In the line inversion driving,an AC common voltage VCOM is supplied to a common electrode which facesa pixel electrode of the liquid crystal cell. In case of a dot inversiondriving, a driving waveform of the test cross-talk data of FIG. 5 isshown in FIG. 7. In the dot inversion driving, the data of which thepolarities are different from each other are supplied to the liquidcrystal cells of adjacent vertical lines, and the data of which thepolarities are different from each other is supplied to the liquidcrystal cells of adjacent horizontal lines. In the dot inversiondriving, the common voltage VCOM is generated in a direct current.

For the cross-talk inspection, the test jig supplies the same mid graylevel data (a mid gray level of A and C areas) to the VDATA1 pad and theVDATA2 pad in the liquid crystal cells Clc of the edge of the pixelmatrix while the test jig supplies the peak white or peak black data (Barea) to the VDATA2 pad in the middle part liquid crystal cells Clc ofthe pixel matrix. In order to select the horizontal line to which thetest gray level data is supplied, the gate high voltage is sequentiallysupplied to the gate lines GL by the gate drive circuit. Then, theliquid crystal cells within the pixel matrix display a window pattern,as shown in FIG. 5, and the light output is automatically detected bythe image pickup device or the expressive capacity of each gray level isinspected with a naked eye.

In the end, according to embodiments of the present invention, theinspection can be done without the data drive circuit even wheninspecting the cross-talk as well as when assessing the expressivecapacity of each gray level. After the inspection, the set of externalcontact pads 1 and the external wire lines 2A to 6 can be removed by ascribing. As described above, the liquid crystal display device and theinspecting method thereof according to embodiments of the presentinvention supplies the data voltages, which are different from eachother, to the pixel matrix array through a separate external pad andwire line for the middle portion of the pixel matrix display, therebymaking it possible to prevent the waste of a data drive circuit.

Although the present invention has been explained by the embodimentsshown in the drawings described above, it should be understood to theordinary skilled person in the art that the invention is not limited tothe embodiments, but rather that various changes or modificationsthereof are possible without departing from the spirit of the invention.Accordingly, the scope of the invention shall be determined only by theappended claims and their equivalents.

1. A liquid crystal display device with data switching thin filmtransistors for inspection, comprising: a pixel matrix where a pluralityof gate lines and a plurality of data lines cross each other and aplurality of liquid crystal cells are arranged; first data switchingthin film transistors respectively and directly connected to data linesof a first data line group of the data lines and directly connected to afirst external wire connected to a first external pad; and second dataswitching thin film transistors respectively and directly connected todata lines of a second data line group of the data lines and directlyconnected to a second external wire connected to a second external pad;wherein the first group of data lines are a bunch of adjacent data linesin the middle of the pixel matrix and the second group of data lines aretwo bunches of adjacent data lines on either sides of the first group ofdata lines, and wherein a first data is supplied to liquid crystal cellsof the middle of the pixel matrix by the first data switching thin filmtransistors and a second data is supplied to liquid crystal cells of thesides of the pixel matrix by the first and second data switching thinfilm transistors when inspecting cross-talk.
 2. The liquid crystaldisplay device according to claim 1, further comprising: gate linedriving thin film transistors respectively connected to the gate lines.3. The liquid crystal display device according to claim 2, wherein thegate line driving thin film transistors and the first and second dataswitching thin film transistors are formed on the same substrate.
 4. Theliquid crystal display device according to claim 1, wherein the firstgroup of data lines are configured so that the first group of data linescan become connected together and the second group of data lines areconfigured so that the second group of data lines can become connectedtogether.
 5. A liquid crystal display device, comprising: a pixel matrixwhere a plurality of gate lines and a plurality of data lines havingfirst and second groups cross each other and a plurality of liquidcrystal cells are arranged; a gate drive circuit for supplying a scanpulse to the gate lines; first data switching thin film transistorsrespectively and directly connected to the first group of the datalines; second data switching thin film transistors respectively anddirectly connected to the second group of the data lines; a firstexternal wire line connected to data input terminals of the first dataswitching thin film transistors; a second external wire line connectedto data input terminals of the second data switching thin filmtransistors; a third external wire line connected to control terminalsof the first and second data switching thin film transistors; a firstexternal pad connected to the first external wire line; a secondexternal pad connected to the second external wire line; and a thirdexternal pad for supplying control data to the third external wire line;wherein the first group of data lines are a bunch of adjacent data linesin the middle of the pixel matrix and the second group of data lines aretwo bunches of adjacent data lines on either sides of the first group ofdata lines, and wherein a first data is supplied to liquid crystal cellsof the middle of the pixel matrix by the first data switching thin filmtransistors and a the second data is supplied to liquid crystal cells ofthe sides of the pixel matrix by the first and second data switchingthin film transistors when inspecting cross-talk, and wherein the firstdata switching thin film transistors are directly connected to the firstexternal wire connected to the first external pad, and the second dataswitching thin film transistors are directly connected to the secondexternal wire connected to the second external pad.
 6. The liquidcrystal display device according to claim 5, further comprising: gateline driving thin film transistors respectively connected to the gatelines; a fourth external wire line connected to the input terminals ofthe gate line driving thin film transistors; a fifth external wire lineconnected to the control terminals of the gate driving thin filmtransistors; a fourth external pad for supplying a gate voltage to thefourth external wire line; and a fifth external pad for supplying acontrol signal to the fifth external wire line.
 7. The liquid crystaldisplay device according to claim 6, wherein the data switching thinfilm transistors, the gate line driving thin film transistors, theexternal wire lines and the external pads are formed on the samesubstrate.
 8. The liquid crystal display device according to claim 5,wherein the first group of data lines are configured so that the firstgroup of data lines can become connected together and the second groupof data lines are configured so that the second group of data lines canbecome connected together.